One aspect of the present invention is a reagent test strip that includes: a) a top support layer including a sample aperture; b) a membrane that includes a reagent system for indicating the concentration of a target; c) a spreading layer; d) a bottom support layer including a measuring port in substantial alignment or approximate alignment with the sample aperture. Preferably, the membrane is affixed to the top support layer. Preferably, the membrane is positioned between the top support layer and the bottom support layer. Preferably, the spreading layer is positioned above the top support layer and in substantial or approximate alignment with the sample aperture. Preferably, a fluid applied to the spreading layer, passes through the sample aperture and contacts the membrane.